Denim, in its modern context of coarse cotton cloth from which jeans are made, is of American origin from the mid-19th century. Today, denims and jeans are interchangeable words but this was not always the case. The origin of the word denim is from the French serge de Nimes, a sort of twill that was made in the French city of Nimes, dating back to the 17th century. The origin of jeans is even older, from the mid-15th century, and derives from the Old French jean fustian, so called because fustian was a type of twilled cotton and jean was the French abbreviation of Genoa because Genoese sailors wore distinctive britches made from this fustian. Jeans only acquired its modern plural form in America during the late 19th century.